Internal Google Eye Tracking Studies
Over at the official Google Blog you can check out eye-tracking studies that Google performed to help optimize their universal search experience. Eye Tracking is a form of usability studies which are designed to track userís eye movements as they navigate websites. Companies like Google leverage Eye Tracking in order to see how users interact with new features before they are applied to production environments.

Based on eye-tracking studies, we know that people tend to scan the search results in order. They start from the first result and continue down the list until they find a result they consider helpful and click it ó or until they decide to refine their query. The heatmap below shows the activity of 34 usability study participants scanning a typical Google results page. The darker the pattern, the more time they spent looking at that part of the page. This pattern suggests that the order in which Google returned the results was successful; most users found what they were looking for among the first two results and they never needed to go further down the page.
SEO TRICKS GUIDE (http://seotricksguide.info/2009/02/internal-google-eye-tracking-studies/)